BTK is a member of the TEC family of non-receptor protein tyrosine kinases, and it is involved in the regulation of B-cell development, activation, and survival through B-cell antigen receptor (BCR) signaling. See W. N. Khan et al., Immunity 3:283-299 (1995); and A. B. Satterthwaite and O. N. Witte, Immunol. Rev. 175:120-127 (2000). Mutation of the gene encoding BTK in humans leads to a condition known as X-linked agammaglobulinemia (XLA), which is characterized by reduced immune function, including impaired maturation of B cells, decreased levels of immunoglobulin and peripheral B cells, diminished T-cell independent immune response, and attenuated calcium mobilization following BCR stimulation. See F. S. Rosen et al., N Engl. J. Med. 333(7):431-440 (1995); and J. M. Lindvall et al., Immunol. Rev. 203:200-215 (2005).
BTK's key role in B-cell development and the BCR signaling pathway suggests that inhibition of BTK may provide therapeutic benefit for the treatment of lymphoma, inflammatory disorders, and autoimmune diseases, among others. Clinical studies involving the depletion of mature B cells via treatment with rituximab indicate that rheumatoid arthritis, systemic lupus erythematosus (SLE), and multiple sclerosis may result from the over expression of B cells. See J. C. Edwards et al., N. Engl. J. Med. 350:2572-81 (2004); C. Favas and D. A. Isenberg Nat. Rev. Rheumatol. 5:711-16 (2009); and S. L. Hauser et al. N. Engl. J. Med. 358:676-88 (2008). Other studies suggest that the BCR pathway may be involved in the survival of tumor cells in non-Hodgkin lymphoma and diffuse large B-cell lymphoma. See R. Küppers, Nat. Rev. Cancer 5:251-62 (2005); and R. E. Davis et al., Nature 463:88-92 (2010). In preclinical studies, BTK-deficient mice have demonstrated decreased disease progression in murine models of SLE and resistance to collagen-induced arthritis. See M. J. Shlomchik et al., J. Exp. Med. 180:1295-1306 (1994); and L. Jansson and R. Holmdahl, Clin. Exp. Immunol. 94(3):459-65 (1993). Furthermore, a selective irreversible BTK inhibitor has been shown to completely suppress collagen-induced arthritis in mice, to inhibit autoantibody production and the development of kidney disease in a mouse model for SLE, and to induce objective clinical responses in dogs with spontaneous B-cell non-Hodgkin lymphoma. See L. A. Honigberg et al., Proc. Natl. Acad. Sci. USA 107(29):13075-80 (2010).
Certain inhibitors of Bruton's tyrosine kinase are described in WO 99/54286 A2, WO 2002/50071 A1, WO 2007/087068 A2, WO 2008/039218 A2, WO 2008/121742 A2, WO 2007/147771 A2, WO 2009/077334 A1, WO 2009/098144 A1, WO 2009/156284 A1, WO 2010/000633 A1, WO 2010/006947 A1, WO 2008/033834 A1, WO 2010/056875 A1, WO 2010/068788 A1, and WO 2010/068810 A2.